Surface and structural analyses of helium ion irradiated beryllium

Abstract

We present the findings of pulsed helium ion irradiation on beryllium that is emitted from a tabletop pulsed ion source. The source delivers a broad range of helium ion energy having most probable energy of 60 keV with a flux of ~1025 m−2s−1. The FESEM micrographs of irradiated samples depict the formation of helium bubbles having tri-modal size distribution. The appearance of larger size bubbles is supposed to be resulted due to Ostwald ripening phenomenon. The calculated rate of irradiation swelling for the beryllium sample due to the development of helium bubbles is found to ~0.24%. The three dimensional AFM micrographs suggest the formation of the hill like structures. An increase in the roughness value of irradiated samples is observed when the helium ion pulse number increases (up to 5 shots) and finally the roughness value decreases for 10 shots helium ion irradiation sample. The XRD patterns reveal the polycrystalline nature of the beryllium samples. In the case of irradiated samples, two feeble planes of beryllium oxide are speculated and most intense peak (002) confirms the formation of compressive stress due to helium ion irradiation.